There was an increased police presence at Poly High School on Wednesday morning after unsubstantiated rumors on social media about a shooting threat. Long Beach February 21, 2018. Photo by Brittany Murray, Press Telegram/SCNG

After 17 people were killed in a Parkland, Fla., school shooting, local students and the public have paid more attention to threats against schools in Southern California.

Since the Feb. 14 Florida shooting, school threats were reported throughout the region including locations in La Palma, Long Beach, Manhattan Beach, Rancho Cucamonga, Studio City, Whittier and more.

Experts say that these threats aren’t new, and it’s difficult to say if there’s been an increase since the Parkland shooting. However, it’s safe to say threats on social media and in conversation are getting more attention from students and the public.

Here’s a timeline of just a handful of local threats that have been reported by officials since Parkland:

Santa Clarita: Saugus High School

Manhattan Beach: Mira Costa High School

A 15-year-old Mira Costa student was arrested after he posted a photo of a gun pointed at students on social media, Manhattan Beach police said. Police said that there was no immediate threat to students, but extra patrols around the city’s schools have been put in place for the next few weeks.

Newport Beach: Corona del Mar High School

Feb. 16

Whittier: El Camino High School

A 17-year-old El Camino High School student was arrested on suspicion of making criminal threats. Police served a search warrant at his house in Norwalk and found a cache of guns, including two AR-15s, two handguns, 90 high-capacity magazines and ammunition.

The teen’s older brother claimed ownership of the weapons. However, one AR-15 was not registered under his name. The teen was not charged for making the threat, but his brother was charged with a misdemeanor count of possession of an assault weapon, the district attorney’s office said.

Feb. 20

Rancho Cucamonga: Vineyard Junior High School

A 13-year-old boy at Vineyard Junior High was arrested on suspicion of making criminal threats after school staff learned of threats made on social media. Officials deemed that there was no threat to the students or staff.

Long Beach and Riverside: Poly High School

Social media rumors warning Poly students of a planned school shooting sparked three separate police investigations in Long Beach, Riverside and San Luis Obispo. The post caused concern for both Long Beach and Riverside Poly High schools and Cal Poly San Luis Obispo. Authorities deemed the threat unfounded. Classes continued as scheduled in Long Beach and Riverside.

Corona: Santiago High School

Rumors of a possible school shooting at Corona’s Santiago High School were deemed false, police said. Corona police learned of the potential threat made on Snapchat, but it was revealed that there was a misunderstanding from the person who saw the post.

Feb. 21

Long Beach: Millikan High School

Long Beach police arrested a student at Millikan High School after classmates overheard the student making a threat to hurt people at the campus, authorities said. The arrest landed on the same day Long Beach school officials beefed up security after online rumors about a possible shooting plot at Long Beach Poly High School were passed around.

Norco: Unnamed college

Investigators arrested a 27-year-old Norco felon and seized several weapons — including a loaded AR-15 — after authorities said the man-made social media threats to shoot up a local college campus. He was arrested on suspicion of making terrorist threats and being a felon in possession of a firearm.

Alhambra: Mark Keppel High School

A Mark Kepple High School student was detained during a police investigation, which was sparked because the student was overheard making comments that may have been perceived as threatening, officials said. The student’s parents cooperated in the investigation and told officials that they keep legal, registered firearms in a secure location in their home. Police determined that the threat was not credible. However, medical issues warranted an ongoing investigation, officials said.

Feb. 22

Long Beach: Tincher Preparatory School

Police arrested a student on suspicion of making threats at Tincher Preparatory School in East Long Beach. A staff member overheard students talking about the threat, and that individual reported the information to police, authorities said. The student was in the eighth grade.

Long Beach: Stanford Middle School

Yucca Valley: Yucca Valley High School

San Bernardino County sheriff’s deputies seized two firearms and arrested a teen after authorities said the student made threats to carry out a shooting at Yucca Valley High School. A juvenile deputy for Yucca Valley spoke to multiple students and teens, who confirmed the threats, officials said.

Studio City and Holmby Hills: Harvard-Westlake School

A social media post that appeared to have been made by former Harvard-Westlake School student and retired NFL offensive lineman Jonathan Martin prompted the school to close its high school in Studio City and its middle school in Holmby Hills. The post showed a gun and tagged former students. School officials decided to close the campuses the following morning. Martin was detained by officials.

Feb. 23

Redondo Beach: Redondo Union High School

Police said that a social media threat of a shooting was not considered credible, but the school did step up security for the day. The threat was circulated to hundreds of students through Snapchat, police said.

San Dimas: San Dimas High School

Deputies were sent to San Dimas High School late at night in response to a call of an armed man, possibly on campus, and found no one, officials said. A student from the school called a classmate and told her she was leaving school after a rehearsal activity and saw a man wave a gun near the trash Dumpsters. The sheriff’s office said, “It was later determined that it was possible the caller saw a school employee emptying the trash.”

Feb. 24

San Bernardino: San Gorgonio High School

A 16-year-old student posted a video on social media showing firearms and said they were a “school shooting starter kit,” officials said. No specific threats were made, police said. However, police did obtain a search warrant and found 11 firearms and hundreds of rounds of ammunition. All firearms and ammunition were seized.

Feb. 25

Norwalk: Cerritos College and Norwalk High School

A false rumor was spread via social media on Sunday night, and it prompted more police presence at both campuses Monday. A Norwalk High School student’s mother reported the threat, which was also made by a student at Norwalk High School, to officials. The Los Angeles County Sheriff’s Department deemed the threat not credible.

Banning: Banning High School

A Snapchat message threatened a school shooting at “BHS,” but police said that it was for Belen High School in New Mexico, not Banning High School. Even then, Banning Police as a precaution said they planned to have extra officers patrolling the Banning High School campus during the week.

Feb. 26

Hemet: Tahquitz High School

Police investigated a social media post that involved Tahquitz High School. School administrators were notified about the “inappropriate” post. Officials did not clarify what the post said or which platform it was posted on.

Torrance: West High School

A West High School student wrote a threat on a restroom wall in hopes of closing the school for the day, officials said. The message said: “Today is Mar Feb 26 Monday sometime this week something will happen at West High School. I wouldn’t doubt this look out West,” and was followed with a smiley face. The female student was arrested on suspicion of vandalism, and police deemed the threat as not credible, officials said.

Chino Hills: Ayala High School

Redlands: Redlands High School

A Redlands High School student reported that she saw a Snapchat message indicating a threat toward a specific student, officials said. Redlands police contacted the male student who was alleged to have made the threat. He denied making any threats and having a Snapchat account. Police deemed the threat to be not credible.

Hemet: Diamond Valley Middle School

A 911 call was made around 1 p.m. to the Hemet Police Department, and a caller said shots were fired on the campus, her sister was crying and she heard two shots. School administrators put the campus on lockdown. Police located the girl who made the call in a field behind the school, officials said. She told investigators what she heard “sounded kinda far away.” No evidence of a shooting was found, officials said.

Feb. 28

Bellflower: St. John Bosco High School

Students reported allegations of a threat to St. John Bosco staff, which prompted school officials to notify parents of “a verbal threat of violence towards the Bosco community.” The threat was later determined to be a dispute among a few students, officials said. Authorities decided to not arrest the student.

Duarte: Duarte High School

A 15-year-old former Duarte High School student was arrested on suspicion of making criminal threats directed toward the campus, authorities said. He made the threats on Instagram over the course of the week and was arrested after midnight at his home in Duarte. The school district reported the posts to officials. Detectives said they believe no further threat exists.

Hemet: Hemet High School

A 16-year-old Hemet High School student was arrested on suspicion of making a threat that was written on a bathroom wall on campus, officials said. The message read, “Hemet High will be shot up on 2-28-18 by a sophomore girl.” The incident was reported to the Riverside County Sheriff’s Department’s Hemet Station. Police said the threat was deemed not credible. Some parents said their children wouldn’t be attending class because of the threat.

Riverside: Villegas Middle School

The principal of Villegas Middle School emailed parents saying a message written on the wall of a girls restroom threatened a campus shooting on March 3. Authorities determined the threat to not be credible because March 3 is a Saturday and school will not be in session, the email said.

March 1

Long Beach: Cubberley Elementary School

An eighth-grader was taken into custody by police after school officials reported a possible threat of violence, officials said. Long Beach Police said officer conducted an investigation and found probable cause to arrest the 13-year-old.

March 2

Hemet: Diamond Valley Middle School

A 16-year-old boy was arrested for allegedly threatening to shoot students and staff. Hemet police said that the boy was standing outside the front of the school when he caught the attention of a campus supervisor. He told the supervisor that he planned to shoot up the school, officials said. He wasn’t armed, but he was questioned and arrested.

March 5

Cypress: Cypress College

Classes at Cypress College were canceled until noon after a former student texted out threats saying he was going to shoot up a campus. The threat was deemed credible but later became not credible, police said. The suspect’s family contacted Whittier police and reported the threat. The 24-year-old suspect was detained in Pico Rivera for a mental-health evaluation. He was banned from the college for a year in 2016. He was seen on campus in recent weeks displaying erratic behavior, officials said.

Fullerton: Parks Junior High

Police detained a 14-year-old student who officials said was overheard threatening to “shoot up” the school the next day. Several students reported hear him say he had access to a handgun, officials said. During a search of the student’s Anaheim home, officers recovered a loaded handgun and ammunition.

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